1. Field of the Invention
This invention relates to a medical imaging apparatus and an ultrasonic imaging apparatus that acquire medical images representing a subject and uses those medical images to obtain the state of motion of the subject. The invention also relates to both a medical image processing apparatus and an ultrasonic image processing apparatus that obtain the state of motion of a subject by using medical images as well as a method of processing medical images.
2. Description of the Related Art
Objective and quantitative functional evaluations of living tissue such as the myocardium are extremely important for diagnosing the living tissue. For example, methods for acquiring image data of a heart using an ultrasonic imaging apparatus to conduct quantitative evaluations based on the image data have been proposed.
As one example, technology (hereinafter referred to as “speckle tracking”, or “ST”) for calculating local wall-motion information including myocardial displacement and deformation while performing tracking of two-dimensional and three-dimensional ultrasonic images by using a local pattern-matching process has been put into practical use according to Japanese published unexamined application 2003-175041 and Japanese published unexamined application 2003-250804.
In the ST method, generally, the endocardial contour and the epicardial contour of the myocardium are defined as the initial tracking positions during the end diastole (the cardiac phase at which the first R wave is detected) or the end systole. Then, in the remaining cardiac phases, by automatically tracking the initial tracking position by using motion vector information acquired through a local pattern-matching process, the endocardial contour and the epicardial contour are tracked in all required time phases.
In the tracking process based on the ST method, it is difficult to estimate the motion vector during diastole (especially early diastole phase E′), when the movement speed of the heart is fastest, and tracking of the contours in cardiac phase E′ deviates easily. Therefore, the applicants of the present application proposed a means of automatically updating the tracking results after cardiac phase E′ onward by manually correcting the contour position to perform retracking in the forward direction when the tracking of the contour deviates after the cardiac phase E′ (Patent Application 2008-114854).
Here, the retracking method proposed in Patent Application 2008-114854 may be referred to as the “ReTrack2” function.
However, tracking errors may occur not only during diastole but also during systole (cardiac phase S′, in which the motion is relatively slow). Sequential corrections of tracking errors occurring during systole or diastole using only the above tracking method (ReTrack2 function) in order to obtain more accurate evaluation results are troublesome and inconvenient.